I think it is very tough to say which turboprop handles turbulence the best since there is no way to accurately measure this. You can't really compare this since turbulence varies so much and there is no telling how much there actually is and how strong it is and how much you will feel it. In your case you may have just flown on a J41 on a day with little chop in the air whereas when you flew the Saab 340 or Dash 8 on a day when the air was very turbulent.
I've never flown on a J41 but I've flown on both the Dash-8 & Saab 340, & ATR-42 many, many times. In each case, I've had flights that have been perfectly smooth and others where I've been bounced all over the place. Ususally cruise is smooth, but climb & descent are all over the place. Even so, my roughest flight ever was on an AA 727-200 from RDU-DTW where we spend the entire flight circling t-storms and crossing a huge frontal boundary. There is no exact way to say which is the best or worst aircraft from a passenger experience. However, the general rule is that jets get bounced around less than props. As for RJ's I dunno, since I've never been on one, but I believe weight is a factor in how much a plane gets bounced around.